1) Field of the Invention
The present invention relates to an activation device for a passenger protection apparatus to be mounted in a vehicle, and more particularly to a technique for activating a passenger protection apparatus at an appropriate timing in response to the occurrence of a roll (rollover) of a vehicle.
2) Description of the Related Art
So far, as a vehicle-mounted passenger protection apparatus for protecting a passenger(s) (including a driver) from the occurrence of a roll of a vehicle, for example, there have been proposed a curtain air bag designed to spread into a curtain-like configuration along a side surface portion of the vehicle, a seat belt with a pretensioner made to take up a seat belt in no time, and an apparatus made to take up a seat belt in a repeated fashion through the use of a motor or the like.
For example, as shown in a block diagram of FIG. 7, a conventional activation system 51 for a passenger protection apparatus is made up of an angular velocity sensor 61 for detecting a roll angular velocity of a vehicle, a control unit 80 including a CPU 80a, a ROM 80b and a RAM 80c, and a curtain air bag 90. When the angular velocity sensor 61 outputs a roll angular velocity signal, a relative angle calculating means 81 makes an integral calculation of a roll angular velocity to obtain a roll relative angle, and a roll judging means 83 makes a decision that the vehicle rolls sideways if the roll angular velocity and the roll relative angle satisfy a predetermined threshold condition, and then a drive control means 84 activates a curtain air bag 90.
However, the optimum activation timing of a curtain air bag can vary in accordance with an open/closed state of a window or a wearing state of a seat belt. That is, the curtain air bag is activated for the purpose of preventing a passenger(s) from being thrown out into the exterior of the vehicle in a case in which a window is in an open state while it is activated for preventing the passenger from being collided against a structure in the interior of the vehicle in a case in which the window is in an closed state, which signifies that the purpose of the activation thereof varies in accordance with an open/closed state of the window. Therefore, for achieving the purpose, there may be a need to activate it at an appropriate timing suitable for that purpose.
On the other hand, depending upon a rolling state of a vehicle (for example, in a case in which the vehicle makes a roll slowly), only the seat belt can prevent the passenger from being thrown out into the exterior of the vehicle even without using the curtain air bag, and the throw-out into the exterior of the vehicle may be preventable by the employment of a seat belt with a pretentioner or an apparatus made to take up a seat belt in a repeated fashion through the use of a motor or the like.